using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;
using StardewValley;

#pragma warning disable 809 // obsolete override of non-obsolete method (this is deliberate)
namespace StardewModdingAPI.Framework.Input
{
    /// <summary>Manages the game's input state.</summary>
    internal sealed class SInputState : InputState
    {
        /*********
        ** Accessors
        *********/
        /// <summary>The cursor position on the screen adjusted for the zoom level.</summary>
        private CursorPosition CursorPositionImpl;

        /// <summary>The player's last known tile position.</summary>
        private Vector2? LastPlayerTile;

        /// <summary>The buttons to press until the game next handles input.</summary>
        private readonly HashSet<SButton> CustomPressedKeys = new HashSet<SButton>();

        /// <summary>The buttons to consider released until the actual button is released.</summary>
        private readonly HashSet<SButton> CustomReleasedKeys = new HashSet<SButton>();

        /// <summary>Whether there are new overrides in <see cref="CustomPressedKeys"/> or <see cref="CustomReleasedKeys"/> that haven't been applied to the previous state.</summary>
        private bool HasNewOverrides;


        /*********
        ** Accessors
        *********/
        /// <summary>The controller state as of the last update, with overrides applied.</summary>
        public GamePadState ControllerState { get; private set; }

        /// <summary>The keyboard state as of the last update, with overrides applied.</summary>
        public KeyboardState KeyboardState { get; private set; }

        /// <summary>The mouse state as of the last update, with overrides applied.</summary>
        public MouseState MouseState { get; private set; }

        /// <summary>The buttons which were pressed, held, or released as of the last update.</summary>
        public IDictionary<SButton, SButtonState> ButtonStates { get; private set; } = new Dictionary<SButton, SButtonState>();

        /// <summary>The cursor position on the screen adjusted for the zoom level.</summary>
        public ICursorPosition CursorPosition => this.CursorPositionImpl;


        /*********
        ** Public methods
        *********/
        /// <summary>This method is called by the game, and does nothing since SMAPI will already have updated by that point.</summary>
        [Obsolete("This method should only be called by the game itself.")]
        public override void Update() { }

        /// <summary>Update the current button states for the given tick.</summary>
        public void TrueUpdate()
        {
            // update base state
            base.Update();

            // update SMAPI extended data
            try
            {
                float scale = Game1.options.uiScale;

                // get real values
                var controller = new GamePadStateBuilder(base.GetGamePadState());
                var keyboard = new KeyboardStateBuilder(base.GetKeyboardState());
                var mouse = new MouseStateBuilder(base.GetMouseState());
                Vector2 cursorAbsolutePos = new Vector2(
                    x: (mouse.X / scale) + Game1.uiViewport.X,
                    y: (mouse.Y / scale) + Game1.uiViewport.Y
                );
                Vector2? playerTilePos = Context.IsPlayerFree ? Game1.player.getTileLocation() : (Vector2?)null;
                HashSet<SButton> reallyDown = new HashSet<SButton>(this.GetPressedButtons(keyboard, mouse, controller));

                // apply overrides
                bool hasOverrides = false;
                if (this.CustomPressedKeys.Count > 0 || this.CustomReleasedKeys.Count > 0)
                {
                    // reset overrides that no longer apply
                    this.CustomPressedKeys.RemoveWhere(key => reallyDown.Contains(key));
                    this.CustomReleasedKeys.RemoveWhere(key => !reallyDown.Contains(key));

                    // apply overrides
                    if (this.ApplyOverrides(this.CustomPressedKeys, this.CustomReleasedKeys, controller, keyboard, mouse))
                        hasOverrides = true;

                    // remove pressed keys
                    this.CustomPressedKeys.Clear();
                }

                // get button states
                var pressedButtons = hasOverrides
                    ? new HashSet<SButton>(this.GetPressedButtons(keyboard, mouse, controller))
                    : reallyDown;
                var activeButtons = this.DeriveStates(this.ButtonStates, pressedButtons);

                // update
                this.HasNewOverrides = false;
                this.ControllerState = controller.GetState();
                this.KeyboardState = keyboard.GetState();
                this.MouseState = mouse.GetState();
                this.ButtonStates = activeButtons;
                if (cursorAbsolutePos != this.CursorPositionImpl?.AbsolutePixels || playerTilePos != this.LastPlayerTile)
                {
                    this.LastPlayerTile = playerTilePos;
                    this.CursorPositionImpl = this.GetCursorPosition(this.MouseState, cursorAbsolutePos, scale);
                }
            }
            catch (InvalidOperationException)
            {
                // GetState() may crash for some players if window doesn't have focus but game1.IsActive == true
            }
        }

        /// <summary>Get the gamepad state visible to the game.</summary>
        public override GamePadState GetGamePadState()
        {
            return this.ControllerState;
        }

        /// <summary>Get the keyboard state visible to the game.</summary>
        public override KeyboardState GetKeyboardState()
        {
            return this.KeyboardState;
        }

        /// <summary>Get the keyboard state visible to the game.</summary>
        public override MouseState GetMouseState()
        {
            return this.MouseState;
        }

        /// <summary>Override the state for a button.</summary>
        /// <param name="button">The button to override.</param>
        /// <param name="setDown">Whether to mark it pressed; else mark it released.</param>
        public void OverrideButton(SButton button, bool setDown)
        {
            bool changed = setDown
                ? this.CustomPressedKeys.Add(button) | this.CustomReleasedKeys.Remove(button)
                : this.CustomPressedKeys.Remove(button) | this.CustomReleasedKeys.Add(button);

            if (changed)
                this.HasNewOverrides = true;
        }

        /// <summary>Get whether a mod has indicated the key was already handled, so the game shouldn't handle it.</summary>
        /// <param name="button">The button to check.</param>
        public bool IsSuppressed(SButton button)
        {
            return this.CustomReleasedKeys.Contains(button);
        }

        /// <summary>Apply input overrides to the current state.</summary>
        public void ApplyOverrides()
        {
            if (this.HasNewOverrides)
            {
                var controller = new GamePadStateBuilder(this.ControllerState);
                var keyboard = new KeyboardStateBuilder(this.KeyboardState);
                var mouse = new MouseStateBuilder(this.MouseState);

                if (this.ApplyOverrides(pressed: this.CustomPressedKeys, released: this.CustomReleasedKeys, controller, keyboard, mouse))
                {
                    this.ControllerState = controller.GetState();
                    this.KeyboardState = keyboard.GetState();
                    this.MouseState = mouse.GetState();
                }
            }
        }

        /// <summary>Get whether a given button was pressed or held.</summary>
        /// <param name="button">The button to check.</param>
        public bool IsDown(SButton button)
        {
            return this.GetState(this.ButtonStates, button).IsDown();
        }

        /// <summary>Get whether any of the given buttons were pressed or held.</summary>
        /// <param name="buttons">The buttons to check.</param>
        public bool IsAnyDown(InputButton[] buttons)
        {
            return buttons.Any(button => this.IsDown(button.ToSButton()));
        }

        /// <summary>Get the state of a button.</summary>
        /// <param name="button">The button to check.</param>
        public SButtonState GetState(SButton button)
        {
            return this.GetState(this.ButtonStates, button);
        }


        /*********
        ** Private methods
        *********/
        /// <summary>Get the current cursor position.</summary>
        /// <param name="mouseState">The current mouse state.</param>
        /// <param name="absolutePixels">The absolute pixel position relative to the map, adjusted for pixel zoom.</param>
        /// <param name="scale">The UI scale applied to pixel coordinates.</param>
        private CursorPosition GetCursorPosition(MouseState mouseState, Vector2 absolutePixels, float scale)
        {
            Vector2 screenPixels = new Vector2(mouseState.X / scale, mouseState.Y / scale);
            Vector2 tile = new Vector2((int)((Game1.uiViewport.X + screenPixels.X) / Game1.tileSize), (int)((Game1.uiViewport.Y + screenPixels.Y) / Game1.tileSize));
            Vector2 grabTile = (Game1.mouseCursorTransparency > 0 && Utility.tileWithinRadiusOfPlayer((int)tile.X, (int)tile.Y, 1, Game1.player)) // derived from Game1.pressActionButton
                ? tile
                : Game1.player.GetGrabTile();
            return new CursorPosition(absolutePixels, screenPixels, tile, grabTile);
        }

        /// <summary>Apply input overrides to the given states.</summary>
        /// <param name="pressed">The buttons to mark pressed.</param>
        /// <param name="released">The buttons to mark released.</param>
        /// <param name="controller">The game's controller state for the current tick.</param>
        /// <param name="keyboard">The game's keyboard state for the current tick.</param>
        /// <param name="mouse">The game's mouse state for the current tick.</param>
        /// <returns>Returns whether any overrides were applied.</returns>
        private bool ApplyOverrides(ISet<SButton> pressed, ISet<SButton> released, GamePadStateBuilder controller, KeyboardStateBuilder keyboard, MouseStateBuilder mouse)
        {
            if (pressed.Count == 0 && released.Count == 0)
                return false;

            // group keys by type
            IDictionary<SButton, SButtonState> keyboardOverrides = new Dictionary<SButton, SButtonState>();
            IDictionary<SButton, SButtonState> controllerOverrides = new Dictionary<SButton, SButtonState>();
            IDictionary<SButton, SButtonState> mouseOverrides = new Dictionary<SButton, SButtonState>();
            foreach (var button in pressed.Concat(released))
            {
                var newState = this.DeriveState(
                    oldState: this.GetState(button),
                    isDown: pressed.Contains(button)
                );

                if (button == SButton.MouseLeft || button == SButton.MouseMiddle || button == SButton.MouseRight || button == SButton.MouseX1 || button == SButton.MouseX2)
                    mouseOverrides[button] = newState;
                else if (button.TryGetKeyboard(out Keys _))
                    keyboardOverrides[button] = newState;
                else if (controller.IsConnected && button.TryGetController(out Buttons _))
                    controllerOverrides[button] = newState;
            }

            // override states
            if (keyboardOverrides.Any())
                keyboard.OverrideButtons(keyboardOverrides);
            if (controller.IsConnected && controllerOverrides.Any())
                controller.OverrideButtons(controllerOverrides);
            if (mouseOverrides.Any())
                mouse.OverrideButtons(mouseOverrides);

            return true;
        }

        /// <summary>Get the state of all pressed or released buttons relative to their previous state.</summary>
        /// <param name="previousStates">The previous button states.</param>
        /// <param name="pressedButtons">The currently pressed buttons.</param>
        private IDictionary<SButton, SButtonState> DeriveStates(IDictionary<SButton, SButtonState> previousStates, HashSet<SButton> pressedButtons)
        {
            IDictionary<SButton, SButtonState> activeButtons = new Dictionary<SButton, SButtonState>();

            // handle pressed keys
            foreach (SButton button in pressedButtons)
                activeButtons[button] = this.DeriveState(this.GetState(previousStates, button), isDown: true);

            // handle released keys
            foreach (KeyValuePair<SButton, SButtonState> prev in previousStates)
            {
                if (prev.Value.IsDown() && !activeButtons.ContainsKey(prev.Key))
                    activeButtons[prev.Key] = SButtonState.Released;
            }

            return activeButtons;
        }

        /// <summary>Get the state of a button relative to its previous state.</summary>
        /// <param name="oldState">The previous button state.</param>
        /// <param name="isDown">Whether the button is currently down.</param>
        private SButtonState DeriveState(SButtonState oldState, bool isDown)
        {
            if (isDown && oldState.IsDown())
                return SButtonState.Held;
            if (isDown)
                return SButtonState.Pressed;
            return SButtonState.Released;
        }

        /// <summary>Get the state of a button.</summary>
        /// <param name="activeButtons">The current button states to check.</param>
        /// <param name="button">The button to check.</param>
        private SButtonState GetState(IDictionary<SButton, SButtonState> activeButtons, SButton button)
        {
            return activeButtons.TryGetValue(button, out SButtonState state)
                ? state
                : SButtonState.None;
        }

        /// <summary>Get the buttons pressed in the given stats.</summary>
        /// <param name="keyboard">The keyboard state.</param>
        /// <param name="mouse">The mouse state.</param>
        /// <param name="controller">The controller state.</param>
        /// <remarks>Thumbstick direction logic derived from <see cref="ButtonCollection"/>.</remarks>
        private IEnumerable<SButton> GetPressedButtons(KeyboardStateBuilder keyboard, MouseStateBuilder mouse, GamePadStateBuilder controller)
        {
            return keyboard
                .GetPressedButtons()
                .Concat(mouse.GetPressedButtons())
                .Concat(controller.GetPressedButtons());
        }
    }
}